Cancer
Cancer is the uncontrolled growth of cells. It is the most feared disease in America, because it is not understood, even though it is not the largest killer. If we understood cancer, we would not be afraid of it. It is estimated that the average individual has a wildly dividing cell six times a day. The immune system recognizes this, kills it, and we never know the difference. When the immune system lets down, even temporarily, and these dividing cells get established to the point that the immune system cannot control them, we have cancer.